Starter

ABSTRACT

A starter is provided that includes a starter motor having an armature core with an armature coil wound therearound and an armature shaft for rotatably holding the armature core. A drive shaft is further provided having a pinion that meshes with a ring gear of an engine. A reduction gear mechanism is interposed between the drive shaft and the armature shaft for reducing the rotation relative to the armature shaft to transmit the reduction rotation to the drive shaft. The reduction gear mechanism has a speed reduction ratio of 6:1 to 10:1.

This application claims benefit of international application PCT/JP9402166, filed Dec. 19, 1994.

TECHNICAL FIELD

The present invention relates to a starter having a speed reduction gearmechanism for starting an engine.

BACKGROUND ART

In the prior art, as disclosed in Japanese Patent Laid-Open No.238171/1990, there has been provided a starter having a planetaryreduction gear mechanism, which has its motor small-sized by setting theplanetary speed reduction ratio to 5.45 at the maximum.

In the aforementioned construction of the prior art, however, only thesize reduction of a motor is intended to achieve by increasing theplanetary reduction ratio, but no consideration has been taken into thesize reduction of the starter in its entirety. Specifically, as thereduction gear ratio increases, the tooth number of an internal gear ofthe planetary reduction gear mechanism increases to enlarge the externaldiameter of the internal gear. As a result, the planetary reduction gearmechanism has its volume increased in proportion to the square of theexternal diameter of the internal gear. Thus, there arises a difficultythat the reduction gear mechanism is large-sized although the motor canbe small-sized by increasing the gear ratio.

As a result of the increase in the reduction gear ratio, moreover, therotational energy E, as expressed by the following equation, of anarmature of the motor will increase in proportion to the square of therotating angular velocity (i.e., R.P.M.) w with respect to an inertialmoment J of the armature:

    E=Jw.sup.2 /2.

As the reduction gear ratio increases, the rotating angular velocity wof the armature may increase to cause a meshing impact at the start ofthe starter or a serious impact torque at the re-meshing time during theinertial rotation of the starter thereby to break the torquetransmitting parts of the starter. Thus, the reduction gear ratioincreasing means is exemplified by the method, in which the gearspecification M (or module) is decreased to increase the reduction gearratio while suppressing the external diameter of an internal gear, but aproblem of the tooth strength is left unsolved. Another method ofincreasing the reduction gear ratio by decreasing the tooth number of asun gear has to make the diameter (as will be called the "deddendumdiameter of the sun gear") of a bearing adjacent to the sun gear smallerthan that of the prior art, thus leaving the strength problem unsolved.

According to the increase in the reduction gear ratio, moreover, theheat radiation from the surface of the starter motor decreases. This isfound from the fact that the heat radiation is proportional to the aream², as generally expressed by the following equation:

    E=C(T/100).sup.4  kj/m.sup.4 h!,

wherein

C: Radiation Constant of Object; and

T: Absolute Temperature.

The present invention has been conceived in view of the background thusfar described and has an object to provide a starter which can besmall-sized in its entirety by clarifying the optimum range of thereduction gear ratio.

DISCLOSURE OF THE INVENTION

In order to achieve the above-specified object, according to the presentinvention, there is provided a starter comprising: a starter motorincluding an armature core having an armature coil wound thereon and anarmature shaft for holding the armature core rotatably; a drive shafthaving a pinion meshing with a ring gear of an engine; and one reductiongear mechanism interposed between the drive shaft and the armature shaftof the starter motor for reducing the rotation of the armature shaft totransmit the reduced rotation to the drive shaft, wherein the reductiongear mechanism has a reduction ratio of 6:1 to 10:1.

In this construction, the reduction ratio of the reduction gearmechanism is set within such an optimum range of 6 to 10 as viewed fromthe volume of the motor and the reduction gear mechanism of the starter,so that the starter can be most effectively reduced in size and weight.

In addition to the aforementioned construction, the armature coilincludes: upper-layer and lower-layer coil members fitted in the slotsof the armature core; first connection portions connected to one end ofthe lower-layer coil member and extending generally in parallel with theaxial end face of the armature core and in the shaft direction; andsecond connection portions connected to one end of the upper-layer coilmember and the other end of the first connection portions and extendinggenerally in parallel with the first connection portions.

According to this construction, the first and second connection portionsare arranged generally in parallel with the end face of the armatureshaft, and the second connection portions are connected to the other endof the first connection portions so that the first and second connectionportions can be accommodated in the small gaps axially protruding fromthe armature core. As a result, a cylindrical commutator and thearmature coil of the prior art can have their inertias reduced mainly asthe armature.

As will be shown in FIG. 6, moreover, the ratio l'/L' in the reactionforce R'=w'l'/L' of the bearing at the sun gear side can be made smallerby that of the cylindrical commutator than the ratio l/L of the priorart, as shown in FIG. 26, so that the bearing reaction force R' can bereduced by the weight of the cylindrical commutator and the value l'/L'.

Owing to the reductions of the inertia of the armature and the bearingreaction force R', therefore, the bearing diameter can be made farsmaller than that of the prior art so that the specification M (ormodule) and the tooth number (or the deddendum diameter) of the sun gearcan be reduced to set the reduction ratio I=6:1 to 10:1 within the rangein which the inner gear has its external diameter smaller than that ofthe motor of the prior art.

As will be shown in FIGS. 6 and 26, furthermore, the bearing span L canbe shortened to L' by a length of the cylindrical commutator so that thedeflection of the shaft can be reduced to take advantages in theinclination and pinch of the bearing and to make a high contribution tothe shortening of the axial length of the motor.

In addition to the foregoing constructions, the starter furthercomprises: insulators interposed between the first connection portionsand the armature core and between said first connection portions and thesecond connection portions; and brushes arranged slidably on the secondconnection portions.

As to the problem of the heat resistance, according to thisconstruction, the first and second connection portions are disposedclose to the side of the armature core through the insulators so thatthe heat to be generated by the resistance between the brushes and thesecond connection portions can be transferred directly to the armaturecore. Thus, it is possible to solve the problem of the reduction of heatresistance of the motor to be caused by the size reduction.

In addition, the starter further comprises a cooling fan for cooling thesliding faces of the starter motor with the brushes.

According to this construction, the cooling fan can reliably cool theresistance heat to be generated at the brushes and the second connectionportions.

In addition, the starter further comprises grooves formed between thesecond connection portions to protrude with respect to the rotatingdirection of the armature shaft so that they act as the cooling fan forproducing a cooling wind when the armature coil rotates.

According to this construction, the cooling fan is exemplified by thegrooves formed between the adjoining second connection portions, and noseparate cooling fan need be added so that the number of parts can bereduced.

In addition, the reduction gear mechanism is a planetary reduction gearmechanism including: a sun gear formed at one end of the armature shaft;a planetary gear mounted on one end of the drive shaft and meshing withthe sun gear; and an internal gear meshing with the planetary gear forforming a stationary side.

According to this construction, the starter can be drastically reducedin size and weight.

In addition, the starter further comprises limit means for limiting thepower supply to the starter motor within a predetermined time period.

According to this construction, limit means is enabled to prevent thepower supply to the starter motor thereby to suppress the abnormaltemperature rise by arranging heat sensing elements such as bimetalelements at portions to receive the heat of the motor such as the motorheating portion, the yoke, the field device, the brush device, the endroom and by using a protector circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side elevation showing the embodiment of a starterof the present invention.

FIGS. 2A and 2B are a front elevation and a partially sectional sideelevation when a pinion rotation regulating member is assembled with apinion portion.

FIG. 3 is a rear elevation of a center bracket.

FIG. 4 is a sectional side elevation of a center bracket.

FIG. 5 is a front elevation of the center bracket.

FIG. 6 is a sectional side elevation of an armature.

FIG. 7 is a top plan view of a core plate.

FIG. 8 is a side elevation of an upper coil bar.

FIG. 9 is a front elevation showing the upper coil bar.

FIG. 10 is a schematic perspective view showing the arranged state ofthe upper coil bar and a lower coil bar.

FIG. 11 is a section of an upper coil member and a lower coil memberfitted in slots.

FIG. 12 is a front elevation of an upper coil end assembled with thecore of an armature.

FIG. 13 is a front elevation of an insulating spacer.

FIG. 14 is a sectional side elevation of a fixing member.

FIG. 15 is a sectional side elevation of an insulating cap.

FIG. 16 is a front elevation of a yoke.

FIG. 17 is an exploded perspective view of a plunger and a stationarycontact of a magnet switch.

FIG. 18 is a perspective view showing the plunger of the magnet switch.

FIG. 19 is a section showing an end frame and a brush spring.

FIG. 20 is a front elevation showing a brush holder.

FIG. 21 is a section taken along line 21--21 of FIG. 20.

FIG. 22 is a section taken along line 22--22 of FIG. 20.

FIGS. 23A, 23B and 23C are electric circuit diagrams showing the workingstates of the pinion.

FIG. 24 is a sectional side elevation showing a cooling air passage.

FIG. 25 is a characteristic chart illustrating the relations between avolume and a reduction ratio.

FIG. 26 is a section showing the armature of the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, a starter of the present invention will be described in connectionwith its embodiment with reference to FIGS. 1 to 25.

The starter is generally divided into: a housing 400 enclosing a pinion200 meshing with a ring gear 100 arranged at an engine and a planetarygear mechanism 300; a motor 500; and an end frame 700 enclosing a magnetswitch 600. In the starter, moreover, the housing 400 and the motor 500are partitioned by a motor partition 800, and the motor 500 and the endframe 700 are partitioned by a brush holding member 900.

Description of Pinion 200!

As shown in FIGS. 1, 2A or 2B, the pinion 200 is formed with a piniongear 210 meshing with the ring gear 100 of the engine.

The pinion gear 210 is formed in its circumference with a pinion helicalspline 211 to be fitted in a helical spline 221 formed in an outputshaft 220. The pinion gear 210 is formed, at the side opposed to a ringgear 100, with an annular flange 213 having a larger diameter than theexternal diameter of the pinion gear 210. This flange 213 is formed allover its outer circumference with teeth 214 having a larger number thanthat of the external teeth of the pinion gear 210. These teeth 214 areprovided for fitting a regulating pawl 231 of a later-described pinionrotation regulating member 230. A washer 215 is made rotatable at therear face of the flange 213 but prevented from axially coming out bybending an annular portion 216, which is formed at the rear end of thepinion gear 210, toward the outer circumference.

On the other hand, the pinion gear 210 is always urged backwards of theoutput shaft 220 by a return spring 240 made of a compression coilspring.

Description of Pinion Rotation Regulating Member 230!

A rotation regulating portion 232 is formed at its one end with theregulating pawl 231 which forms a regulating portion axially extendingto engage with the numerous teeth 214 formed in the flange 213 of thepinion gear 210. The regulating pawl 231 is fitted in the teeth 214 ofthe pinion gear 210 and is folded radially inwards to have an L-shapedsection.

Here will be described the operations of the pinion rotation regulatingmember 230. A string member 680 is transmission means for transmittingthe operation of the magnet switch 600 to the regulating pawl 231. Thestring member 680 is caused by the operation of the magnet switch 600 topull the rotation regulating portion 232 downwards thereby to establishthe engagement between the regulating pawl 231 and the teeth 214 of theflange 213 of the pinion gear 210. At this time, a return spring portion233 has its one end portion 236 abutting against a position regulatingshelf 362 to bend the return spring portion 233. Since the regulatingpawl 231 engages with the teeth 214 of the pinion gear 210, the piniongear 210 is moved forwards, when turned through an armature shaft 510 ofthe motor 500 and the planetary reduction mechanism 300, along thehelical spline 221 of the output shaft 220. When the pinion gear 210comes into abutment with the ring gear 100 so that its forward movementis blocked, the pinion rotation regulating member 230 itself is bent bythe further rotating force of the output shaft 220 so that the piniongear 210 is slightly rotated to mesh with the ring gear 100. As thepinion gear 210 moves forwards, the regulating pawl 231 goes out ofengagement with the teeth 214 so that the regulating pawl 231 drops atthe back of the flange 213 of the pinion gear 210 to have its front endabutting the rear face of the washer 215 hereby to prevent the piniongear 210 from being retracted by the rotation of the ring gear 100 ofthe engine.

Simultaneously as the operation of the magnet switch 600 is interruptedto stop the downward pull of the rotation regulating portion 232 by thestring member 680, the rotation regulating portion 232 is returned toits original position by the action of the return spring portion 233.

Description of Pinion Retaining Ring 250!

The pinion retaining ring 250 is fixed in the annular groove which isformed around the output shaft 220 to have a square section. This pinionretaining ring 250 is shaped by rounding a steel bar having a squaresection and is formed on its two ends with generally S-shapedcorrugations 251 (i.e., examples of engaging means), one of which hasits ridge engaging with the recess of the other and the other of whichhas its ridge engaging with the recess of the former.

Description of Planetary Gear Mechanism 300!

The planetary gear mechanism 300 is reduction means for reducing therotational speed of the later-described motor 500 to augment the outputtorque of the motor 500, as shown in FIG. 1. This planetary gearmechanism 300 is composed of: a sun gear 310 (having a tooth number ofZs=8) formed on the outer circumference of the front side of thearmature shaft 510 (as will be described later) of the motor 500; threepairs of planetary gears 320 (having a tooth number of Zp=25) maderotatable around the sun gear 310; a planet carrier 330 made integralwith the output shaft 220 for supporting the planetary gears 320rotatably around the sun gear 310; and an internal gear 340 (having atooth number Zi=58) made of a resin into a cylindrical shape meshingwith the outer circumferences of the planetary gears 320.

The reduction ratio of the planetary gear mechanism 300 will bedescribed on the basis of the characteristic diagram plotting thereduction ratio on the abscissa and the volume on the ordinate of FIG.25. Here: letter D indicates the external diameter of the yoke 501 ofthe starter shown in FIG. 1; letter L the axial length of the yoke 501;and the volume V₁ of the starter motor is expressed by V₁ =πD² L/4. Onthe other hand, the volume V₂ of the planetary gear mechanism 300 isexpressed, if the internal gear 340 has an external diameter d and anaxial length l, by V₂ =πd² l/4. Hence, the volume V_(T) =V₁ +V₂influencing the starter is expressed by:

    V.sub.T =V.sub.1 +V.sub.2 =πD.sup.2 L/4+πd.sup.2 l/4.

It is apparent from FIG. 25 that the volume V₁ of the starter decreasesas the reduction ratio rises, as indicated by the dotted curve, whereasthe volume V₂ of the planetary gear mechanism 300 gradually increases asthe reduction ratio rises, as indicated by the single-dotted curve. As aresult, the total volume V_(T) takes its minimum at a reduction ratio(in the vicinity of 8) and then rises again at a higher reduction ratio.

In order to reduce the total volume V_(T) of the starter, it iseffective to set the reduction ratio to 6:1 to 10:1. Specifically, thereduction ratio around 8:1 is effective. The planetary gear mechanismdescribed above satisfies the meshing condition of the planetary gear ofZs+Zi/N (i.e., the number of planetary gears)=Rectification to determinethe following reduction ratio:

    I=Zi/Zs+1, I=8.25.

In the optimum range of reduction ratio of 6:1 to 10:1, as illustratedin the chart of FIG. 25 of the relation between the motor size at therated output of 12V (volts)-0.6 KW (kilowatts) to 3.0 KW 24 V-2.0 KW to5.5 KW and the volume of the reduction gear mechanism, I=8.25 isselected as the most optimum value. Moreover, the result of selectingthe gears used in the embodiment is enumerated in Table 1.

                  TABLE 1                                                         ______________________________________                                                    Zi          Di   Maximum                                                                              Deddendum Diameter                        M     Zs    (mm)   I    (mm) Zi (mm)                                                                              Zs (mm)                                   ______________________________________                                        1.25  11    /      /    /    less than                                                                            11.9                                            10    /      /    /    or     10.6                                            9     39     5.33 56   equal to                                                                             9.4                                             8     40     6.0  57   41     8.1                                       1.1   11    /      /    /    less than                                                                            10.45                                           10    /      /    /    or     9.35                                            9     45     6.0  52   equal to                                                                             8.25                                            8     46     6.75 57   47     7.15                                      1.0   11    52     5.72 58   less than                                                                            9.5                                             10    50     6.0  55   or     8.5                                             9     51     6.66 58   equal to                                                                             7.6                                             8     52     7.5  58   52     6.5                                       0.9   11    55     6.0  56   less than                                                                            8.55                                            10    56     6.6  57   or     7.65                                            9     57     7.33 58   equal to                                                                             6.75                                            8     58     8.25 58   58     5.85                                      0.8   12    63     6.25 56   less than                                                                            8.4                                             11    64     6.8  57   or     7.6                                             10    62     7.2  56   equal to                                                                             6.8                                             9     63     8.0  56   65     6.0                                             8     64     9.0  57          5.2                                       ______________________________________                                    

The restricting conditions are: the external diameter of the motor 1 isset to 68 from the standpoint of reducing the size of the starter; andthe external diameter Dl of internal gear 22 is set to 58. Moreover, asun gear 12 is set to have an ordinarily manufacturable value Zs=8, astress distribution satisfied to reduce the inertia of armature 540, alower limit M module up to 0.8, a deddendum diameter Zs to more than 5(mm) and a transposition to 0.5.

Description of Overrunning Clutch 350!

The overrunning clutch 350 is so supported as to rotate the internalgear 340 only in one direction (to rotate in response to the revolutionof the engine). This overrunning clutch 350 is composed of a clutchouter 351 made integral with the front side of the internal gear 340 toform a first cylindrical portion, an annular clutch inner 352 formed atthe rear face of a center bracket 360 to form the stationary sidecovering the front of the planetary gear mechanism 300 and a secondcylindrical portion arranged to confront the inner circumference of theclutch outer 351, and rollers 353 fitted in a roller path formed at aninclination in the inner circumference of the clutch outer 351.

Description of Center Bracket 360!

The center bracket 360 is arranged in the rear side of the housing 400.The housing 400 and the center bracket 360 are connected by a ringspring 390, which has its one end retained by the housing 400 and itsother end retained by the center bracket 360, so that the rotationalreaction to be received by the clutch inner 352 forming part of theoverrunning clutch 350 may be absorbed by the ring spring 390 andprevented from being transmitted directly to the housing 400.

Description of Planet Carrier 330!

The planet carrier 330 is equipped at its rear end with a flangedprojection 331 radially extending for supporting the planetary gear 320.In this flanged projection 331, there is fixed a pin 332 extendingbackwards for supporting the planetary gear 320 rotatably through ametal bearing 333.

Moreover, the planet carrier 330 is rotatably supported by a housingbearing 440 having its front end portion fixed in the front end of thehousing 400, and a center bracket bearing 370 fixed in an innercylindrical portion 365 of the inner circumference of the center bracket360.

This planet carrier 330 is formed at its front end with an annulargroove 334, in which is fitted a stop ring 335. Between this stop ring335 and the front end of the inner cylindrical portion 365, there isinterposed a washer 336 which is made rotatable with respect to theplanet carrier 330. When the stop ring 335 comes into abutment againstthe front end of the inner cylindrical portion 365 through the washer336, the planet carrier 330 is regulated from moving backwards.Moreover, the center bracket bearing 370 supporting the rear side of theplanet carrier 330 is formed at its rear end with a flanged portion 371which is interposed between the rear end of the inner cylindricalportion 365 and the flanged projection 331. When this flanged projection331 comes into abutment against the rear end of the inner cylindricalportion 365 through a flanged portion 371, the planet carrier 330 isregulated from moving forwards.

Incidentally, the planet carrier 330 is formed in its rear face with anaxially extending recess 337. A shaft 510 has its front end rotatablysupported through a planet carrier bearing 380 which is arranged in thatrecess 337.

Description of Housing 400!

The housing 400 supports the output shaft 220 in the housing bearing440, which is fixed in the front end of the housing 400, and is equippedwith a water shielding wall (as shown in FIG. 1) for minimizing the gapbetween the housing 400 and the external diameter of the pinion gear 210below the opening 410 so as to minimize invasion of rain droplets or thelike from an opening 410.

Description of Shutter 420!

The shutter 420 is made of a resin material (e.g., nylon) and mountedaround the output shaft 220. The shutter 420 is composed of a ringmember 421 clamped between the return spring 240 and the pinion gear210, and a water shielding portion 422 for opening/closing the opening410 of the housing 400. This water shielding portion 422 is bent, asshown in FIG. 1, to be fitted from the two sides in two slide grooves(not shown) which are so formed in the lower portion of the front end ofthe housing 400 as to extend in the axial direction. As a result, thewater shielding portion 422 can axially move together with the ringmember 421 with respect to the housing 400. Incidentally, a washer 480is interposed between the shutter 420 and the pinion gear 210.

The shutter 420 operates in the following manner. As the starter isstarted to move the pinion gear 210 forwards along the output shaft 220,the ring member 421 is moved forwards together with the pinion gear 210.Then, the water shielding portion 422 is moved forwards together withthe ring member 421 to open the opening 410 of the housing 400. When thestarter is stopped to move the pinion gear 210 backwards along theoutput shaft 220, the ring gear 421 is moved backwards together with thepinion gear 210. Then, the water shielding portion 422 is also movedbackwards together with the ring member 421 to close the opening 410 ofthe housing 400. As a result, while the starter is not operating, theshutter 420 acting as the opening/closing means prevents the raindroplets, which are scattered by the centrifugal force of the ring gear100, with the water shielding portion 422 from invading the housing 400.

Description of Motor 500!

The motor 500 is enclosed by the yoke 501, the motor partition 800 andthe later-described brush holding member 900. Incidentally, the motorpartition 800 accommodates the planetary gear mechanism 300 togetherwith the center bracket 360 and acts to prevent the lubricating oil inthe planetary gear mechanism 300 from invading the motor 500.

The motor 500 is constructed of, as shown in FIG. 1, of: the armature540 composed of the armature shaft 510, and the armature core 520 and anarmature coil 530 fixed on the armature shaft 510 and made rotatabletogether; and stationary magnetic poles 550 for rotating the armature540. These stationary magnetic poles 550 are fixed on the innercircumference of the yoke 501.

Description of Armature Shaft 510!

The armature shaft 510 is rotatably borne by the planet carrier bearing380 in the rear portion of the planet carrier 330 and a brush holdingmember bearing 564 fixed in the inner circumference of the brush holdingmember 900. The armature shaft 510 has its front end inserted in theplanetary gear mechanism 300 and formed on its outer circumference withthe sun gear 310 of the planetary gear mechanism 300.

Description of Armature Core 520!

The armature core 520 is prepared by laminating a number of core plates521, as shown in FIG. 7, and by press-fitting the armature shaft 510 inthe hole 522 which is formed in the center of the laminate. The coreplate laminate 521 is formed by pressing thin steel sheets and byinsulating its surfaces. The core plate laminate 521 is formed in theradially internal side (or around the hole 522) with a plurality ofpunched holes 523 for lightening the core plate laminate 521 itself.This core plate laminate 521 is formed in its outer circumference with aplurality of (e.g., twenty five) slots 524 for receiving the armaturecoil 530. Moreover, the outer circumferential end of the core platelaminate 521 is formed between the individual slots 524 with fixingpawls 525 for fixing the armature coil 530 in the slots 524. The fixingpawls 525 will be described in the description of means for fixing thefollowing armature coil 530.

Description of Armature Coil 530!

The armature coil 530 adopted in the present embodiment is adouble-layer coil which is prepared by radially laminating a pluralityof (e.g., twenty five) upper-layer coil bars 531 and lower-layer coilbars 532 of the same number as that of the upper-layer coil bars 531.Moreover, these individual upper-layer coil bars 531 and lower-layercoil bars 532 are combined to have their end portions electricallyconnected to constitute an annular coil.

Description of Upper-Layer Coil Bar 531!

The upper-layer coil bar 531 is made of a material having an excellentconductivity (e.g., copper) and is formed with: an upper-layer coilmember 533 extending in parallel with the stationary magnetic poles 550and held on the outer circumferential side of the slots 524; and twoupper-layer coil ends 534 bent inwards from the two ends of theupper-layer coil member 533 and extending perpendicularly to the axialdirection of the armature shaft 510 to form a second connection portion.Incidentally, the upper-layer coil member 533 and the two upper-layercoil ends 534 may be formed: integrally by the cold-casting; by thepressing into the C-bent shape; or by the seaming technique of weldingthe upper-layer coil member 533 and the two upper-layer coil ends 534made separate.

The upper-layer coil member 533 is a straight bar having a squaresection, as shown in FIGS. 8 to 11, and is so forced together with alater-described lower-layer coil member 536 into the slots 524 that itis covered with an upper-layer insulating film 125 (e.g., a thin film ofa resin such as nylon or paper), as shown in FIG. 11.

Of the two upper-layer coil ends 534, as shown in FIG. 10, oneupper-layer coil end 534 is inclined at the forward side with respect tothe rotating direction whereas the other upper-layer coil end 534 isinclined at the backward side with respect to the rotating direction.These two upper-layer coil ends 534 are radially inclined at an equalangle with respect to the upper-layer coil member 533 and are formedinto an identical shape. As a result, the upper-layer coil bar 531 takesits identical shape even after it is turned by 180 degrees on theupper-layer coil bar 531. In short, the two upper-layer coil ends 534are made identical to provide an excellent workability when theupper-layer coil bar 531 is assembled with the armature core 520.

Of the two upper-layer coil ends 534, the upper-layer coil end 534, aslocated at the side of the magnet switch 600, comes into direct abutmentwith later-described brushes 910 to feed the armature coil 530 with theelectric power. For this, at least the surface of the upper-layer coilends 534, against which the brushes 910 are to abut, is smoothed. Thestarter of the present embodiment need not be equipped with anyindependent commutator for energizing the armature coil 530. In short,the independent commutator can be eliminated to reduce the number ofparts and steps of manufacturing the starter thereby to suppress theproduction cost. Since, moreover, the starter need not be arrangedtherein with the independent commutator, another effect is that thestarter can be axially small-sized.

Furthermore, the upper-layer coil ends 534 come into direct abutmentagainst the brushes 910 so that the heat generated by the slidingcontact between the upper-layer coil ends 534 and the brushes 910propagates from the up per-layer coil ends 534 to the upper-layer coilmember 533, the armature core 520 and the armature shaft 510. Since,however, the armature coil 530, the armature core 520 and the armatureshaft 510 have larger heat capacities than those of the independentcommutator of the prior art, the sliding contact portions between theupper-layer coil ends 34 and the brushes 910 can be kept at a lowtemperature.

The upper-layer coil ends 534 are shaped, as shown in FIG. 12, toradially diverge and to have substantially equal circumferential lengthsfrom the inner to outer circumferences. This considerably enlarges thecontact areas between the upper-layer coil ends 534 and the brushes 910to abut against each other. As a result, the brushes 910 get liable tohave their heat dissipating to the coil bar so that their temperaturecan be suppressed to a very low level. Incidentally, FIG. 12 illustratesthe shape of the upper-layer coil ends 534 schematically, and theirnumber is not equal to that of the slots 524 of FIG. 8.

Moreover, grooves 535 formed between the individual upper-layer coilends 534 to abut the brushes 910 are shaped so helical as to sweep backmore in the rotating direction as they go radially outward, as shown inFIG. 12. Thanks to the swept-back shape of the grooves 535, the brushes910 come into gradual abutment with the inner sides of the upper-layercoil ends 34 having the lower rotational speed to the outer sides havingthe higher rotational speed. As a result, the brushes 910 to abut theupper-layer coil ends 534 can be prevented from jumping at theupper-layer coil ends 534.

As, moreover, the armature coil 530 is rotated, a centrifugal wind isestablished radially outward by the grooves 535. This centrifugal wind,as is established by the rotations of the individual grooves 535 of theindividual upper-layer coil ends 534 to abut against the brushes 910 isused to cool the heat generated by the sliding contacts between thebrushes 910 and the upper-layer oil ends 534 and to discharge thebrushed powder to the outside, as will be described hereinafter. The twoupper-layer coil ends 534 are formed on their confronting outercircumferences with axially protruding projections 534a having a smallerdiameter. These projections 534a are arranged between the upper-layercoil ends 534 and later-described lower-layer coil ends 537 so that theyare fitted in holes 561 formed in an insulating spacer 560 forinsulating the upper-layer coil ends 534 and the lower-layer coil ends537 (as shown in FIG. 13).

Description of Lower-Layer Coil Bar 532!

The lower-layer coil bar 532 is made, like the upper-layer coil bar 531,of a material having an excellent conductivity (e.g., copper) and isformed with: the lower-layer coil member 536 extending in parallel withthe stationary magnetic poles 550 and held on the inner side of theslots 524; and two lower-layer coil ends 537 bent inwards from the twoends of the lower-layer coil member 536 and extending perpendicularly tothe axial direction of the shaft 510 Lo form a first connection portion.Incidentally, the lower-layer coil member 536 and the two lower-layercoil ends 537 may be formed, as in the upper-layer coil bar 531:integrally by the cold-casting; by the pressing into the C-bent shape;or by the seaming technique of welding the lower-layer coil member 536and the two lower-layer coil ends 537 made separate.

Incidentally, the insulations between the individual upper-layer coilends 534 and the individual lower-layer coil ends 537 are retained bythe insulating spacer 560, and the insulations between the individuallower-layer coil ends 537 and the armature core 520 are retained by aninsulating ring 590 made of a resin (e.g., nylon or phenolic resin).

The lower-layer coil member 536 is a straight bar having a squaresection, as shown in FIGS. 8 to 11, and is forced together with theupper-layer coil member 533 into the slots 524. Incidentally, thelower-layer coil member 536 is so fitted in the slots 524 together withthe upper-layer coil member 533 covered with the upper-layer insulatingfilm 125, while being covered with a lower-layer insulating film 105(made of nylon or paper).

Of the two lower-layer coil ends 537, one lower-layer coil end 537, aslocated at the front side of the starter, is inclined in the directionopposed to that of the upper-layer coil end 534 whereas the otherlower-layer coil end 537 at the rear side is also inclined in thedirection opposed to that of the upper-layer coil end 534. These twolower-layer coil ends 537 are radially inclined at an equal angle withrespect to the lower-layer coil member 537 and are formed into anidentical shape. As a result, like the upper-layer coil bar 531, thelower-layer coil bar 531 takes its identical shape even after it isturned by 180 degrees on the lower-layer coil bar 532. In short, the twolower-layer coil ends 537 are made identical to provide an excellentworkability when the lower-layer coil bar 532 is assembled with thearmature core 520.

The two lower-layer coil ends 537 are formed at their innercircumferential end portions with lower-layer inner extensions 539extending in the axial direction. The lower-layer inner extensions 539have their outer circumferences fitted in the recesses 562, which areformed in the inner circumferences of the insulating spacer 560, andoverlapped on and electrically and mechanically sealed by the welding tothe inner circumferences of upper-layer inner extensions 538 at the endportions of the upper-layer coil ends 534. Incidentally, the lower-layerinner extensions 539 have their inner circumferences insulated andarranged from the armature shaft 510.

On the other hand, the two upper-layer coil ends 534 are formed at theirinner circumferential end portions with the upper-layer inner extensions538 extending in the axial direction. These upper-layer inner extensions538 have their inner circumferences overlapped on and electrically andmechanically sealed by the welding to the outer circumference of thelower-layer inner extensions 539 which are formed at the inner ends ofthe later-described lower-layer coil bar 532. Moreover, the upper-layerinner extensions 538 have their outer circumferences abutting throughinsulating caps 580 on the inner faces of the outer circumferentialannular portions 571 of stationary members 570 press-fitted in thearmature shaft 510.

Description of Insulating Spacer 560!

The insulating spacer 560 is a thin sheet ring made of a resin (e.g., anepoxy resin, a phenolic resin or nylon) and formed in its outercircumferential side, as shown in FIG. 13, with the plurality of holes561, in which are fitted the projections 534a of the individualupper-layer coil ends 534. On the other hand, the insulating spacer 560is formed in its inner circumference with recesses 562, in which arefitted the lower-layer inner extensions 539 of the lower-layer coil ends537. These holes 561 and recesses 562 of the insulating spacer 560 areused to position and fix the armature coil 530, as will be describedhereinafter.

Description of Fixing Member 570!

The fixing member 570 is an iron annular member which is composed, asshown in FIG. 14, of: an inner circumferential annular portion 572 to bepress-fitted on the armature shaft 510; a regulating ring 573 extendingperpendicularly to the axial direction for blocking the upper-layer coilends 534 and the lower-layer coil ends 537 from axially extending; andthe outer circumferential portion 571 enclosing the upper- layer innerextensions 538 of the upper-layer coil ends 534 for preventing theinternal diameter of the armature coil 530 from being extended by thecentrifugal force. Incidentally, this fixing member 570 has thedisc-shaped insulating cap 580 made of resin (e.g., nylon) andsandwiched between the upper-layer coil ends 534 and the lower-layercoil ends 537, as shown in FIG. 15, so as to ensure the insulationsbetween the upper-layer coil ends 534 and the lower-layer coil ends 537.

The fixing member 570 arranged at the front side of the starter comesinto abutment with the rear face of the motor partition 800 adjacent tothe front of the fixing member 570 to act as a thrust receiving portionfor regulating the forward movement of the armature 540. On the otherhand, the fixing member arranged at the rear side of the starter comesinto the front face of the brush holding member 900 adjacent to the rearof the fixing member 570 to act as a thrust receiving portion forregulating the backward movement of the armature 540.

Thus, each fixing member 570 for fixing the inner end portion of thearmature coil 530 acts as the thrust receiving portion of the armature540 so that no other thrust receiving portion of the armature 540 needbe provided. As a result, the numbers of parts and assembling steps ofthe starter can be reduced.

Description of Means for Fixing Armature Coil 530!

The means for positioning and fixing the upper-layer coil bars 531 andthe lower-layer coil bars 532 of the armature coil 530 on the armaturecore 520 is composed of: the slots 524 and the fixing pawls 525 of thearmature core 20; the holes 561 and the recesses 562 of the insulatingspacer 560, and the fixing member 570 to be press-fitted on the armatureshaft 510.

The slots 524 of the armature core 520 receives the upper-layer coilmembers 533 and the lower-layer coil members 536, and the fixing pawls525 are folded radially inwards, as indicated by arrows in FIG. 11, sothat the upper-layer coil members 533 and the lower-layer coil members536 are firmly fixed in the Individual slots 524 and are prevented frommoving radially outward from the insides of the slots 524 even theyreceive the centrifugal force. Incidentally, the upper-layer coilmembers 533 have their outer circumferential surfaces insulated by thetwo layers of the lower-layer insulating film 125 and the upper-layerinsulating film 105 so that it can be sufficiently insured even if thefixing pawls 525 are forcibly folded radially inwards.

The recesses 562 in the inner circumference of the insulating spacer 560are fitted on the lower layer inner extensions 539 of the lower-layercoil ends 537 to position the lower-layer coil ends 537 and to receivethe centrifugal force applied to the lower-layer coil ends 537 therebyto prevent the lower-layer coil ends 537 from moving radially outward.

The holes 561 in the outer circumferential side of the insulating spacer560 are fitted on the projections 534a of the upper-layer coil ends 534to position the upper-layer coil ends 534 and to receive the centrifugalforce applied to the upper-layer coil ends 534 thereby to prevent theupper-layer coil ends 534 from moving radially outward.

The fixing member 570 protects the upper-layer inner extensions 538 andthe lower-layer inner extensions 539 from the surroundings to move theradially inner portion of the armature coil 530 from being movedradially outward by the centrifugal force.

Moreover, the fixing member 570 regulates the movements of the axial endportions of the upper-layer inner extensions 538 and the lower-layerinner extensions 539 thereby to prevent the axial size of the armaturecoil 530 from increasing. Incidentally, if the upper-layer coil ends 534and the lower-layer coil ends 537 are axially elongated while thestarter is being used, a space estimating the deformation in advance hasto be retained in the starter. Thanks to the action of the fixing member570, however, the upper-layer coil ends 534 and the lower-layer coilends 537 are prevented from being axially elongated, and any space neednot be prepared in the starter of the present embodiment so that thestarter can have its axial size reduced.

Description of Yoke 501!

The yoke 501 is a cylinder shaped by rounding a steel sheet, as shown inFIG. 16, and is formed in its circumference with a plurality of grooves502 which are extended axially and recessed radially inwards. Thesegrooves 502 are used to arrange through-bolts and to position thestationary magnetic poles 550 on the inner circumference of the yoke510.

Description of Stationary Magnetic Poles 550!

The stationary magnetic poles 550 are exemplified by permanent magnetsin the present embodiment and are composed of a plurality of (e.g., six)main magnetic poles 551 and interpole magnetic poles 552 interposedbetween those main magnetic poles 551, as shown in FIG. 16.Incidentally, the permanent magnets of the stationary magnetic poles 550may be replaced by field coils for generating magnetic forces whensupplied with an electric power.

The main magnetic poles 551 are positioned by the two ends of the insidewalls of the recesses 502 of the aforementioned yoke 510 and are fixedtogether with the interpole magnetic poles 552 between them in the yoke501 by a fixing sleeve 553 arranged on the inner circumference of thestationary magnetic pole 550.

Description of Magnet Switch 600!

As shown in FIGS. 1, 17 and 18, the magnet switch 600 is held by thelater-described brush holding member 900 and arranged in thelater-described end frame 700 such that it is fixed generallyperpendicularly to the armature shaft 510. Moreover, the magnet switch600 is arranged perpendicularly to the axial direction of the armatureshaft 510.

The magnet switch 600 moves a plunger 610 upwards, when energized, tobring two contacts (i.e., a lower movable contact 611 and an uppermovable contact 612) into sequentially contact with the head 621 of aterminal bolt 620 and the abutting portion 631 of a stationary contact630. Incidentally, the terminal bolt 620 is connected with the not-shownbattery cable.

The magnet switch 600 is constructed in a bottomed cylindrical magnetswitch cover 640 made of a magnetic material (e.g., iron). This magnetswitch cover 640 is prepared by pressing a soft steel sheet, forexample, into the shape of a cup having a hole 641 at its bottom centerfor receiving the plunger 610 movably in the vertical directions.Moreover, the magnet switch cover 640 has its upper opening closed witha stationary core 642 made of a magnetic material (e.g., iron).

The stationary cover 642 is composed of an upper larger-diameter portion643, a lower intermediate-diameter portion 644 and a lowersmaller-diameter portion 645 and is fixed in the upper opening of themagnet switch cover 640 by caulking the upper end of the magnet switchcover 640 inwards with the outer circumference of the larger-diameterportion 643. An attraction coil 650 has its upper end mounted around theintermediate-diameter portion 644. On the outer circumference of thesmaller-diameter portion 645 of the stationary core 642, there ismounted the upper end of a compression coil spring 660 for biasing theplunger 610 downwards.

The attraction coil 650 is attraction means for attracting the plunger610 by generating a magnetic force when energized. This attraction coil650 is equipped with a sleeve 651 which has its upper end mounted on theintermediate-diameter portion 644 of the stationary core 642 and coversthe plunger 610 vertically slidably. This sleeve 651 is prepared byrolling a thin sheet of a non-magnetic material (e.g., copper, brass orstainless steel) and is equipped at its upper and lower ends withinsulating washers 652 of a resin. The sleeve 651 is wrapped between thetwo insulating washers 652 with a (not-shown) insulating film made of athin resin (e.g., a cellophane or nylon film) or paper, and thisinsulating film is further wound with a predetermined number of turns ofthin enamel wires to construct the attraction coil 650.

The plunger 610 is made of a magnetic metal (e.g., iron) and is formedgenerally into the shape of a cylinder having an upper smaller-diameterportion 613 and a lower larger-diameter portion 614. Thesmaller-diameter portion 613 has the lower end of the compression coilspring 660 mounted thereon, and the larger-diameter portion 614 isrelatively elongated in the axial direction and held vertically movablyin the sleeve 651.

On the upper side of the plunger 610, there is fixed a plunger shaft 615extending upwards from the plunger 610. The plunger shaft 615 protrudesupward from the through hole which is formed at the center of thestationary core 642. The upper movable contact 612 is carried on theplunger shaft 615 above the stationary core 642 to slide verticallyalong the plunger shaft 615. This upper movable contact 612 isregulated, as shown in FIG. 17, from moving upwards from the upper endof the plunger shaft 615 by a snap ring 616 attached to the upper end ofthe plunger shaft 615. As a result, the upper movable contact 612 ismade vertically slidable along the plunger shaft 615 between the snapring 616 and the stationary core 642. Incidentally, the upper movablecontact 612 is biased upwards at all times by a contact pressure spring670 which is made of a leaf spring attached to the plunger shaft 615.

The upper movable contact 612 is made of a metal having an excellentconductivity such as copper and has its two ends brought, when movedupward, into abutment against the two abutting portions 631 of thestationary contact 630. On the upper movable contact 612, moreover, theindividual lead wires 910a of the paired brushes 910 are fixedelectrically and mechanically by the caulking or welding. In the grooveof the upper movable contact 612, moreover, there is inserted and fixedelectrically and mechanically the end portion of a resistor 617 forproviding a plurality of (e.g., two in the present embodiment)restricting means.

Incidentally, the individual lead wires 910a of the brushes 910 arefixed electrically and mechanically in the upper movable contact 612 bythe caulking or welding. However, the upper movable contact 612 and theindividual lead wires 910a of the brushes 910 may be integrally formed.

The resistor 617 is constructed of a plurality of turns of metal wirehaving a high resistance for allowing the motor 500 to rotate at a lowspeed at the initial stage of the starter operation. On the other end ofthe resistor 617, there is fixed by the caulking or the like the powermovable contact 611 which is positioned below the head 621 of theterminal bolt 620.

The lower movable contact 611 is made of a metal having an excellentconductivity such as copper and is brought into abutment against theupper face of the stationary core 642, when the magnet switch 600 is OFFso that the plunger 610 takes its lower position, and into abutmentagainst the head 621 of the terminal bolt 620 before the upper movablecontact 612 comes into the abutment against the abutting portion 631 ofthe stationary contact 630 when the resistor 617 is carried upwards bythe plunger shaft 615.

The plunger 610 is formed in its lower face with a recess 682 forreceiving a ball member 681 attached to the rear end of the stringmember 680 (e.g., wire). The recess 682 has its inner circumferentialwall internally threaded, as at 683. Into this internal thread 683,there is fastened a fixing screw 684 for fixing the ball member 681 inthe recess 682. The string member 680 has its length adjusted byadjusting the insertion of the fixing screw 684 into the internal thread683. Incidentally, the length of the string member 680 is adjusted suchthat the regulating pawl 231 of the pinion rotation regulating member230 is fitted in the teeth 214 of the outer circumference of the piniongear 210 when the lower movable contact 611 comes into abutment with theterminal bolt 620. Incidentally, the internal thread 683 and the fixingscrew 684 constitute an adjusting mechanism.

Description of End Frame 700!

The end frame 700 is a magnet switch cover made of a resin (e.g., aphenolic resin) having the magnet switch 600 accommodated therein.

The end frame 700 is formed on its back face with spring holding pillars710 which are protruded forwards according to the positions of thebrushes 910 for holding compression coil springs 914 to bias the brushes910 forwards.

Moreover, the compression coil springs 914 are arranged, as shown inFIG. 1, at the outer circumferential side with respect to the axialdirection of the plunger 610 of the magnet switch 600.

The terminal bolt 620 is a bolt of iron, which is inserted from theinside of the end frame 700 and protruded backwards of the end frame 700and which is formed at its front side with the head 621 to be broughtinto abutment against the inner face of the end frame 700. Moreover, theterminal bolt 620 is fixed on the end frame 700 by fixing a caulkingwasher 622 on the terminal bolt 620 protruded backwards from the endframe 700. The stationary contact 630 made of copper is fixed by thecaulking on the front end of the terminal bolt 620. The stationarycontact 630 is formed with one or more (i.e., two in the presentembodiment) abutting portions 631 disposed on the upper end of theinside of the end frame 700, and the upper movable contact 612 to bevertically moved by the operation of the magnet switch 600 can bebrought at its upper face into abutment against the lower face of theabutting portions 631.

Description of Brush Holding Member 900!

The brush holding member 900 performs not only the role to partition theinside of the yoke 501 and the inside of the end frame 700 whilesupporting the rear end of the armature shaft 510 rotatably through thebrush holding member bearing 564 but also the roles to act as the brushholder, to hold the magnet switch 600 and to act as a pulley 690 forguiding the string member 680. Incidentally, the brush holder 900 isformed with the not-shown hole for guiding the string member 680therethrough.

The brush holder 900 is a partition shaped by casting a metal such asaluminum and is formed, as shown in FIGS. 20 to 22, with a plurality of(e.g., two at the upper and lower sides in the present embodiment) brushholding holes 911 and 912 for holding the brushes 910 axially. The upperbrush holding holes 911 are the holes for holding the brush 910 toreceive the plus voltage and hold the brush 910 (as shown in FIG. 21presenting a section taken along line 21--21 of FIG. 20 and in FIG. 22presenting a section taken along line 22--22 of FIG. 20) throughinsulating cylinders 913 made of a resin (e.g., nylon or a phenolicresin). On the other hand, the lower brush holding holes 912 are theholes for holding the brush 910 to be grounded to the ground and holdthe brush 910 directly therein.

Since the brushes 910 are thus held by the brush holder 900, it isunnecessary to provide the starter with any independent brush holder. Asa result, it is possible to reduce the number of parts and assemblingsteps of the starter.

Moreover, the brushes 910 are urged by the compression coils 914 tobring their front end faces onto the rear faces of the upper-layer coilends 534 at the rear side of the armature coil 530.

Incidentally, the upper brush 910 has its lead wires 910a connectedelectrically and mechanically by the seaming technique such as thewelding or caulking to the upper movable contacts 612 to be moved by themagnet switch 600. On the other hand, the lower brush 910 has its leadwires 910a connected electrically and mechanically by the caulking to arecess 920 formed in the rear face of the brush holding member 900.Incidentally, the present embodiment is equipped with a pair of lowerbrushes 910 which are connected to one lead wire 910a, which has itscenter caulked in the recess 920 of the rear face of the brush holdingmember 900.

The brush holding member 900 is formed on its back face with twopedestals 930 for holding the front face of the magnet switch 600, andtwo stationary pillars 940 for embracing the magnet switch 600.

The pedestals 930 are contoured to the magnet switch 600 having acylindrical shape so that they may snugly abut the magnet switch 600. Onthe other hand, the two stationary pillars 940 hold the magnet switch600 by caulking their individual rear ends while the magnet switch 600abutting against the pedestals 930.

The brush holding member 900 is formed on the lower side of its rearface with a pulley holding portion 950 for holding the pulley 690 forchanging the moving direction of the string member 680 from the verticaldirection to the axial direction of the magnet switch 600.

The brush holding member 900 is formed on its rear face with a holdingportion 960 for holding a not-shown temperature switch for protectionfrom an overheat. This holding portion 960 holds the temperature switchbetween the upper brush holding holes 911 and the lower brush holdingholes 912 and in the vicinity of the magnet switch 600. Incidentally,the temperature switch turns OFF the magnet switch 600, when apredetermined temperature is reached, to interrupt the power supply tothe starter motor thereby to protect the starter.

The brush holding member 900 has its front face disposed in the vicinityof the rear face of the upper-layer coil ends 534 to abut the brushes910. As a result, the centrifugal wind established by the rotations ofthe grooves 535 between the upper-layer coil ends 534 is forcibly guidedradially outward. In short, the centrifugal wind is established betweenthe upper-layer coil ends 534 at the rear side and the brush holdingmember 900.

The starter is formed, as shown in FIG. 24, with cooling air passagesfor introducing the air into the inside between the upper-layer coilends 534 at the rear side and the brush holding member 900 and forreleasing the centrifugal wind to the outside of the starter.

This cooling air passage is formed of: an inlet port 970 opened in theinner circumferential portion of the brush holding member 900 forintroducing the air from the inside of the end frame 700 into the insidebetween the upper-layer coil ends 534 at the rear end and the brushholding member 900; brush holding member communication holes 980 formedin the end frame 700 and in the upper circumference of the brush holdingmember 900 and communicating with the gaps between the main poles 551 inthe yoke 501; the gaps 590 formed between the main magnetic poles 551and communicating with those brush holding member communicating holes980; motor partition communication holes 810 formed in the uppercircumference of the motor partition 800 and communication with the gaps590 between the main poles 551; notches 364 formed in the upper side ofthe center bracket 360 and communicating with the motor partitioncommunication holes 810; and the inside of the housing 400. Thus, theair sucked from the opening 410 of the housing 400 is guided to theinside between the upper-layer coil ends 534 at the rear side and thebrush holding member 900 in the course of the inside of the housing 400,the notches 364 in the upper side of the center bracket 360, the motorpartition communication holes 810, the gaps 590 between the mainmagnetic poles 551, the brush holding member communication holes 980,the inside of the end frame 700 and the inlet port 970.

The centrifugal wind established between the upper-layer coil ends 534at the rear side and the brush holding member 900 is discharged, afterhaving cooled down the sliding faces and the peripheries of the brushes910, together with the brushed powder to the outside of the starter froma discharge hole 503 formed in the lower end of the yoke 501.

Since the upper-layer coil ends 534 acting as the commutator act as thecentrifugal fan to establish the centrifugal wind, it is possible tokeep the temperature of the sliding portions between the upper-layercoil ends 534 and the brushes 910 to a low level. Moreover, the brushedpowder produced as a result of the wear of the brushes 910 is carried bythe centrifugal wind to the discharge hole 503 and discharged therefromto the outside of the starter thereby to prevent the troubles due to thebrushed powder.

Operations of Embodiment!

Next, the operations of the aforementioned starter will be describedwith reference to electric circuit diagrams of FIGS. 23A to 23C.

When a key switch 10 is set to the start position by the driver, theelectric power is fed from a battery 20 to the attraction coil 650 ofthe magnet switch 600. When the attraction coil 650 is energized, theplunger 610 is attracted by the magnetic Force generated by theattraction coil 650 so that it is lifted from its lower position.

As the plunger 610 starts its rise, the upper movable contact 612 andthe lower movable contact 611 are lifted by the rising plunger shaft615, and the string member 680 also has its rear end lifted. When therear end of the string member 680 rises, the front end of the same ispulled downwards so that the pinion rotation regulating member 230 ismoved downwards. The lower movable contact 611 is brought into abutmentagainst the head 621 of the terminal bolt 620 (as shown in FIG. 23A) bythe downward movement of the pinion rotation regulating member 230, whenthe regulating pawl 231 is fitted in the teeth 214 on the outercircumference of the pinion gear 210. The terminal bolt 620 is suppliedwith the voltage of the battery 20 so that its voltage is applied to theupper brush 910 in the course of the lower movable contact 611 theresistor 617 the upper movable contact 612 the lead wire 911. In short,the low voltage through the resistor 617 is applied through the upperbrush 910 to the armature coil 530. Since, moreover, the lower brush 910is always grounded to the ground through the brush holding member 900,the low voltage is applied to the armature coil 530 which is constructedin the coil shape by combining the individual upper-layer coil bars 531and the individual lower-layer coil bars 532. Then, the armature coil530 generates a relatively weak magnetic force, which acts upon (i.e.,attracts or repulses) the magnetic force of the stationary magnetic pole550 so that the armature 540 is rotated at a low speed.

As the armature shaft 510 rotates, the planetary gear 320 of theplanetary gear mechanism 300 is rotationally driven by the sun gear 310at the front end of the armature shaft 510. In case the rotating torqueof the planetary gear 320 to drive the ring gear 100 rotationallythrough the planet carrier 330 is to be imparted to the internal gear340, this internal gear 340 has its rotation regulated by the action ofthe overrunning clutch 350. In short, the internal gear 340 does notrotate, the planet carrier 330 is decelerated by the rotation of theplanetary gear 320. When the planet carrier 330 rotates, the pinion gear210 will rotate but has its rotation regulated by the pinion rotationregulating member 230 so that it moves forwards along the helical spline221 of the output shaft 220.

As the pinion gears 210 moves forwards, the shutter 420 also movesforwards to open the opening 410 of the housing 400. As a result of thisforward movement, the pinion gear 210 comes into complete meshingengagement with the ring gear 100 of the engine until it comes intoabutment with the pinion retaining ring 250. As the pinion gears 210advances, moreover, the regulating pawl 231 comes out of engagement withthe teeth 214 of the pinion gear 210 until its front end drops at therear side of the washer 215 which is disposed on the rear face of thepinion gear 210.

With the pinion gear 210 being in the forward position, on the otherhand, the upper movable contact 612 comes into abutment against theabutting portion 631 of the stationary contact 630. Then, the batteryvoltage of the terminal bolt 620 is applied directly to the brushes 910in the course of the upper movable contact 612 and the lead wire 911. Inshort, the armature coil 530 composed of the individual upper-layer coilbars 531 and the individual lower-layer coil bars 532 is fed with thehigh current to generate an intense magnetic force thereby to rotate thearmature 540 at a high speed.

The rotation of the armature shaft 510 is decelerated by the planetarygear mechanism 300 so that the planet carrier 330 is rotationally drivenby the increased rotating torque. At this time, the pinion gear 210 hasits front end brought into abutment with the pinion retaining ring 250so that it rotates together with the planet carrier 330. Since,moreover, the pinion gear 210 is in meshing engagement with the ringgear 100 of the engine, it drives the ring gear 100, i.e., the outputshaft of the engine rotationally.

Next, when the engine is started to rotate its ring gear 100 faster thanthe pinion gear 210, a retracting force is generated in the pinion gear210 by the action of the helical spline. Since, however, the pinion gear210 is blocked from its backward movement by the rotation regulatingpawl 231 having dropped at the back of the pinion gear 210, the enginecan be started without fail while preventing the premature disengagementof the pinion gear 210 (as shown in FIG. 23B).

When the started engine has its ring gear 100 rotated faster than thepinion gear 210, this pinion gear 210 is rotationally driven by the ringgear 100. Then, the rotating torque having been transmitted from thering gear 100 to the pinion gear 210 is further transmitted through theplanet carrier 330 to the pin 332 supporting the planetary gear 320. Inother words, the planetary gear 320 is driven by the planet carrier 330.Then, a torque reversed from that for the engine starting time isapplied to the internal gear 340 so that the overrunning clutch 350allows the ring gear 100 to rotate. More specifically, if the torquereversed from that for the engine starting time is applied to theinternal gear 340, the roller 353 of the overrunning clutch 350 comesout of the recess of the clutch inner 352 to allow the rotation of theinternal gear 340.

In short, the relative rotation of the ring gear 100 of the startedengine to drive the pinion gear 210 rotationally is absorbed by theoverrunning clutch 350 so that the armature 540 is not rotationallydriven by the engine.

After the engine has been started, the key switch 10 is moved out of thestart position by the driver to stop the power supply to the attractioncoil 650 of the magnet switch 600. When the power supply to theattraction coil 650 is stopped, the plunger 610 is returned backdownward by the action of the compression coil spring 660.

Then, the upper movable contact 612 leaves the abutting portion 631 ofthe stationary contact 630, and the lower movable contact 611 thenleaves the head 621 of the terminal bolt 620 to interrupt the powersupply to the upper brush 910.

When the plunger 610 is returned downwards, the pinion rotationregulating member 230 is returned upwards by the action of its returnspring portion 236 so that the regulating pawl 231 leaves the back ofthe pinion gear 210. Then, the pinion gear 210 is returned backwards bythe action of the return spring 240 to come out of meshing engagementwith the ring gear 100 of the engine and to bring its rear end intoabutment against the flange-shaped protrusion 222 of the output shaft220. In short, the pinion gear 210 is returned to the stage before thestart of the starter (as shown in FIG. 23C).

As a result that the plunger 610 is returned downwards, moreover, thelower movable contact 611 comes into abutment with the upper face of thestationary core 642 of the magnet switch 600 so that the lead wire 910aof the upper brush 910 is turned conductive in the course of the uppermovable contact 612, the resistor 617, the lower movable contact 611,the stationary core 642, the magnet switch cover 640 and the brushholding member 900. In short, the upper brush 910 and the lower brush910 are short-circuited through the brush holding member 900. Meanwhile,an electromotive force is generated in the armature coil 530 by theinertial rotation of the armature 540. Moreover, this electromotiveforce is short-circuited through the upper brush 910, the brush holdingmember 900 and the lower brush 910 so that the braking force is appliedto the inertial rotation of the armature 540. As a result, the armature540 is abruptly stalled.

Effects of Embodiment!

Since, in the embodiment thus far described, the lower-layer coil ends537 and the upper-layer coil ends 534 forming the first and secondconnecting portions are held in abutment against the end face of thearmature core 500 through the insulators, the inertias of thecylindrical commutators and the armature coils in the prior art arereduced to reduce the inertia drastically as that of the armature 540.As a result, while the pinion gear 210 is meshing with the ring gear100, the impact torque at the time of inertial rotation can be reducedto reduce the module of the used gear to M=0.9. At the same time, thereaction force R, of the armature bearing 570 can be reduced by theweight of the cylindrical commutator of the prior art, and its supportdistribution can be reduced to l'/L', as compared with the value l/L ofthe prior art, to reduce the diameter of the bearing. As a result, thesun gear 310 can have its tooth number reduced to Zs=8 (i.e., thededdendum diameter of=5.85), and the reduction ratio can be set toI=8.25. Hence, the motor volume can be reduced to I=8.25, as comparedwith I=6 or less in the prior art, so that the motor can be small-sized.

Due to the grooves 535 in the gaps of the individual upper-layer coilends 534, moreover, the centrifugal wind is produced radially outward bythe grooves 535 of the upper-layer coil ends 534 as the armature coil530 rotates. Moreover, the air thus established by the individualgrooves 35 of the individual upper-layer coil ends 534 abutting againstthe brushes 910 and sucked from the opening 410 of the housing 400 isguided to the inside between the upper-layer coil ends 534 at the rearside and the brush holding member 900 in the course of the inside of thehousing 400, the notches 364 in the upper side of the center bracket360, the motor partition communication holes 810, the gaps 590 betweenthe main magnetic poles 551, the brush holding member communicationholes 980, the inside of the end frame 700 and the inlet port 970.

The centrifugal wind established between the upper-layer coil ends 534at the rear side and the brush holding member 900 is discharged, afterhaving cooled down the sliding faces and the peripheries of the brushes910, together with the brushed powder to the outside of the starter froma discharge hole 503 formed in the lower end of the yoke 501.

Since the upper-layer coil ends 534 acting as the commutator act as thecentrifugal fan to establish the centrifugal wind, it is possible tokeep the temperature of the sliding portions between the upper-layercoil ends 534 and the brushes 910 to a low level.

As a result, the shortage of the thermal radiation, which is caused atthe speed reduction ratio I=8.25 by the less motor surface area thanthat of the prior art, is solved by the air-cooling effect so that thesize of the motor can be reduced with a sufficient heat resistingperformance.

Moreover, the means for restricting the power supply to the startermotor 500 within a predetermined time period by sensing the heatliberated from the motor may be exemplified by another protecting unitwhich is arranged with heat sensing elements such as bimetal elements inthe vicinity of the heat sensing portions, the brush device 900, thefield device 550, the yoke 501 and the end frame 700 to turn OFF thepower supply of the magnet switch 600 to the attraction coil 650, whenthe motor temperature reaches a predetermined level, thereby to stop thepower supply to the starter motor. The bimetal elements are of theworking type but may be exemplified by the self-holding type in whichthe OFF state is held when the element is opened. In case theaforementioned protecting device is used together, the armature having agenerally helical commutator in the armature core need not be usedtogether, but the armature of the prior art may be used. Still moreover,a timer unit may be assembled in the starter control circuit to restrictthe time period for the power supply to the starter.

Thus, according to the present invention, the starter can have its sizeand weight remarkably reduced, as compared with the starter of the priorart, by clarifying the optimum range of 6 to 10 for the high reductionratio range I=6 or more, unlike the prior art, and by setting I=8.25.

Since the starter can be drastically small-sized according to thepresent embodiment, the starter can be effectively mounted in the deadspace, which cannot mount it in the prior art, such as the engineflywheel or the oil pan below the engine.

INDUSTRIAL APPLICABILITY

As has been described hereinbefore, the starter according to the presentinvention can be utilized as a starter having a reduction gear mechanismfor starting an internal combustion engine.

We claim:
 1. A starter comprising:a starter motor including an armaturecore having an armature coil wound thereon and an armature shaft forholding said armature core rotatably; a drive shaft having a pinionmeshing with a ring gear of an engine; and a reduction gear mechanisminterposed between said drive shaft and said armature shaft of saidstarter motor for reducing the rotation relative to said armature shaftto transmit the reduced rotation to said drive shaft, wherein saidreduction gear mechanism having a speed reduction ration of 6:1 to 10:1,wherein said reduction gear mechanism is a planetary reduction gearmechanism including:a sun gear formed at one end of said armature shaft;a planetary gear mounted on one end of said drive shaft and meshing withsaid sun gear; and an internal gear meshing with said planetary gear forforming a stationary side, wherein said reduction gear mechanism is of asingle unit type and the planetary gear transmits rotation of saidarmature shaft to said drive shaft.
 2. A starter according to claim 1,wherein said armature coil includes:upper-layer and lower-layer coilmembers fitted in slots of said armature core; first connection portionsconnected to one end of said lower-layer coil member and extendinggenerally in parallel with an axial end face of said armature core andin said shaft direction; and second connection portions connected to oneend of said upper-layer coil member and the other end of said firstconnection portions and extending generally in parallel with said firstconnection portions.
 3. A starter according to claim 2, furthercomprising:insulators interposed between said first connection portionsand said armature core and between said first connection portions andsaid second connection portions; and brushes arranged slidably on saidsecond connection portions.
 4. A starter according to any of the claims1 to 3, further comprising:a cooling fan for cooling sliding faces ofsaid starter motor with said brushes.
 5. A starter according to claim 4,further comprising:grooves formed between said second connectionportions to protrude with respect to a rotating direction of saidarmature shaft so as to act as said cooling fan for producing a coolingwind when said armature coil rotates.
 6. A starter according to any ofthe claims 1 to 3, further comprising:limit means for limiting the powersupply to said starter motor within a predetermined time period.
 7. Astarter according to claim 1, wherein said reduction gear mechanism hasa speed reduction ratio of about 8.25:1.
 8. A starter according to claim1, wherein the reduction ratio is set so that the total volume V_(T),=V₁+V₂, where V₁ =volume of the starter motor and V₂ =the volume of theplanetary gear mechanism, is substantially at a minimum.
 9. A starteraccording to claim 1, satisfying the following relationship:I=Zi/Zs+1where Zi=the number of teeth of the internal gear, Zs=the number ofteeth of the sun gear, and I=the reduction ratio.
 10. A starter as inclaim 9, wherein the Zi=58 and Zs=8.
 11. A starter as in claim 1,wherein an external diameter of the motor is set to 68 mm and anexternal diameter of the internal gear is set to 58 mm.